Use the C++ language so this can compile (#353)

Author: keryell

lib/polygeist/Ops.cpp

@@ -2329,7 +2329,7 @@ class SelectOfExt final : public OpRewritePattern<arith::SelectOp> {
 
     auto fitsIn = [&](auto i, int width) {
       // if there is nothing in the bits that would be discarded
-      return !((~((static_cast<typeof i>(1) << width) - 1)) & i);
+      return !((~((static_cast<decltype(i)>(1) << width) - 1)) & i);
     };
 
     // Truncate the other non-extended const but only if the original constant